public class Sqrt {

	public static void main(String[] args) {
		double c = Double.parseDouble(args[0]);
		double epsilon = 1e-15;  // relative error tolerance
		double t = c;   		 // estimate of the square root of c

		// repeatedly apply Newton update step until desired precision is achieved
		while (Math.abs(t - c/t) > epsilon*t) {
			t = (c/t + t) / 2.0;
		}

		System.out.println(t);
	}
}